Overhead cranes

ABSTRACT

An overhead crane has two lifting drums rotating simultaneously to lift a load, the drive to the drums being in the form of a closed kinematic chain in which that part normally running idle includes a gear wheel mounted so that its axis is displaced when load is transmitted through it due to a failure in the other part of the chain. Said displacement operates a warning circuit whereby an indication of the failure is provided while the drive continues to be transmitted through said gear wheel.

United States Patent Fischer 1 Nov. 6, 1973 15 1 OVERHEAD CRANES3,004,445 10 1961 Mondon 74 411 x 3,086,402 4/1963 Erard [75] lnventor:Herbert Fischer, Wolverhampton, 3,175,110 3/1965 Kohlhagen England3,244,020 4/1966 Breuer 74 411 1 1 Assignool l r p -J Thompson FOREIGNPATENTS OR APPLICATIONS Gaieshead, Cmmty 1,226,267 10/1966 Germany .1212 21 Durham, England 281,051 12/1964 Netherlands 212/21 [22] Filed:Oct. 29, 1971 Primary Examiner-Ev0n C. Blunk [2]] Appl' 193,645Assistant ExaminerJames L. Rowland Att0rneyErnest A. Greenside [30]Foreign Application Priority Data Nov. 3, 1970 Great Britain 52,204/70[57] ABSTRACT Nov. 10, 1970 Great Britain 53,452 70 An overhead crane hw lifting drums rotating simultaneously to lift a load, the drive to thedrums being [52] US. Cl. 212/10, 74/41 1 in the form of a closed k nem ihain in which that [51 1 Int. Cl B66x 17/00 p r normally unn ng idleincludes a gear wheel [58] Field of Search 212/10, 11, 1822; mounted soha i xi is displaced'when load is trans- 254/184; 74/41 1, 406; 192/150mitted through it due to a failure in the other part of the chain. Saiddisplacement operates a warning circuit [56] Referen Cit d whereby anindication of the failure is provided while UNITED STATES PATENTS thedrive continues to be transmitted through said gear 1,606,106 11/1926Shutt 212 22 wheel 2,702,995 3/1955 Biedess 74/411 X 9 Claims, 3 DrawingFigures SHEET 1 BF 2 PATENTEUNM 6 1973 OVERHEAD CRANES This inventionrelates to overhead cranes.

Where overhead cranes are intended for lifting heavy and potentiallydangerous loads, for example, ladles containing molten steel, two basicqualities that are especially important are reliability andavailability.

Reliability includes the adequacy of the design to ensure the functionand performance of the crane without failure, and this is a qualitywhich every crane is expected to'possess as a matter of'course. However,there is no absolute reliability, and failures can occur.

A crane will possess a maximum of availability if maintenance andbreakdowns cause a minimum of interference in the required duty of thecrane.

Commonly an overhead crane intended for lifting a heavy load, such as ahot-metal ladle, is provided with two lifting drums, or two series oflifting drums, each drum or series having one of two ropes or two seriesof ropes, each of the two ropes orseries of ropes being attachable toopposite sides of the load.

It is known to provide an arrangement in which the two drums or seriesof drums (for convenience of description, this specification will referto two drums, one for each lifting rope), the driving motor or motors(there may be one motor driving both drums, or each drum may have itsown driving motor) and the gears form a closed kinematic chain orcircuit. This includes two intermediate spur gear wheels, or amultiplicity of pairs of such wheels, between the drum spur wheels, andalthough these intermediate spur wheels are in loose mesh, one withanother, they are unloaded during normal operation of the crane.

The failure of any part of this chain or circuit (other than the spurgear wheels on the drum) still maintains the connection between themotor or motors and the rope drums, since the intermediate spur wheelsbecome loaded and their teeth move into bearing contact, so that the twodrums can continue to operate, both drums being driven through one andthe same path round the kinematic chain or circuit, which path does notinclude the failed part. When two driving motors are used, one for eachdrum, both drums can be driven by one motor if the other motor fails.Thus, there is provided a safety means which will prevent the loadfalling in the event of any such failure.

However, hitherto it sometimes has been difficult for the crane operatorto know that a failure in the said circuit has occurred, because thecrane continues to operate the load, apparently normally. The object ofthis invention is to provide means for indicating to the operator thatsuch a failure has occurred.

According to this invention, in a drive means for at least one pair ofrope drums of a crane, said drive means being in the form of a kinematicchain and comprising intermediate gear wheels forming a part of saidchain between gear wheels rotatably secured to said pair of drums, oneof said intermediate gear wheels is arranged to mesh with respectivegear wheels at substantially diametrically opposite regions of said onegear wheel and is mounted so as to be displaceable substantiallyperpendicularly to the diametrical plane between said opposite regions,means being provided to operate a warning device when the application ofa torque load to said intermediate gear wheel displaces it in saiddirection.

Thereby, in the event of a failure in the drive to one of the said ropedrums, the load, or part of the load, will be transmitted through theintermediate gear wheels, and the axis of said one intermediate spurgear wheel will be displaced towards one or the other of its endpositions and cause the said warning device to be operated.

The invention will be more particularly described with reference to theaccompanying drawings FIG. 1 is a diagrammatic plan view of an overheadcrane showing the drive arrangement to a pair of rope drums of thecrane; and

FIGS. 2 and 3 are similar diagrammatic elevations of the crane of FIG.1, showing the assembly of rope drum spur gear wheels and intermediatespur gear wheels, and incorporating alternative forms of the invention.

In FIG. 1 there can be seen trolley 2 of the crane having wheels 3mounted on a gantry structure 4 of the crane along which the trolleyperforms cross-transverse motions under the action of respective drivemeans 6. The structure 4 is itself able to transport the trolley inlongitudinal traverse motions but the drive means for this purpose isnot illustrated as the manner of traverse drive of gantry cranes is wellknown in the art and does not form any part of the novelty of thepresent invention.

On the trolley 2 are mounted two rope drums 11 and 12 on respectiveshafts 13 and 14 and the shafts have respective gear wheels 15 and 16secured to them. The gear wheel 15 is driven by a motor 17 throughreduction and other gearing 18, a shaft 19 and a pinion 20, the pinion20 meshing with the gear wheel 15. Similarly, the gear wheel 16 isdriven by a motor 21 through reduction and other gearing 22, a shaft 23and a pinion 24, the pinion 24 meshing with the gear wheel 16.

The two motors 17 and 21 are interconnected by a shaft 25.

Between the two drum wheels 15 and 16 there is a pair of spur gearwheels 26 and 27 which are in mesh with each other and with the gearwheels 15 and 16, respectively. Braking devices 28, 29, 30 and 31 areprovided at required positions in the drive transmission.

This arrangement provides a closed kinematic chain or circuit. In theevent of the failure of any part of the circuit, other than the two drumgear wheels 15 and 16, the two. drums can still be driven by one or bothof the motors 17, 21, the drive transmission path being clockwise orcounterclockwise in the circuit, depending upon the position of thefailed part. In such an event, the two intermediate spur gear wheels 26and 27 will become loaded.

In FIG. 2 there is shown the assembly of the gear wheels 15, 26, 27 and16, and pinions 20 and 24, the gear wheels 26 and 27 being in loosemeshing engagement, or normal tooth-contact meshing engagement with eachother and with the gear wheels 15 and 16. Between the bearing 32 of thejournal of the gear wheel 27 and the support in the frame 10 for thebearing, there is provided a slot 33 which is perpendicular to thediameter of the wheel 27 joining the positions of meshing of the wheel27 with the two wheels 26 and 16; in this illustrated example saidperpendicular attitude is vertical.

Thus, in the event of the load, or part of the load being transmittedthrough the wheels 26 and 27, the load on the wheel 27 will move itbodily up or down, depending on which direction the load passes, in thevertical path indicated by the arrows 34, 35, and the bearing 32 willmove to the top or bottom end of the slot 33 where a limit switch 35, orother switching device, will be located and will close an electriccircuit containing an audible or a visual warning device 36. Themovement is limited in extent so that the wheel 27 is not displaced outof mesh with the wheels l6 and 26 as it transmits the drive between theadjacent wheels 16 and 26.

FIG. 3 shows an alternative arrangement to that in FIG. 2. In thisexample, the bearing 32 mounted in an elastic collar or bush 37 so thatwhen the load or part of the load is transmitted through the wheels 26and 27, as hereinbefore described, the collar or bush will be compressedto allow the wheel 27 to move up or down.

What I claim and desire to secure by Letters Patent IS l. in a cranehaving at least one pair of rope drums in turn having gear wheels linkedby a kinematic gear chain including a series of cooperating elements,the improvements consisting in that said kinematic gear chain is aclosed circuit kinematic chain drive having two series of components onopposite sides of and interconnected by a coupling shaft, each series ofcomponents, beginning at a point most distant from said coupling shaftand in a direction toward said coupling shaft, including first gearmeans, motor means for driving said gear means, and brake means forbraking the drive in the event of motor failure; and second gear meanscomprising at least in part said gear wheels of said rope drums andincluding standby means intermediate said gear wheels, said second gearmeans being operatively coupled to said first gear means of each saidseries of components for driving connection therewith, said standbymeans of said second gear means being mounted in relation to said gearwheels to actively drive said gear wheels and to support the torque loadonly upon failure within said closed circuit kinematic chain drive of atleast one of said series of components of each of said series, saidstandby means comprising for this purpose intermediate gear wheel meanshaving a displaceable mounting providing for rotation of said firstintermediate gear wheel means about a first axis during normal operationof said closed circuit kinematic chain, said mounting beingautomatically displaced, upon failure of one of said series ofcomponents, in a direction transverse to the direction of meshing extentof said intermediate gear wheel means to orient said mounting forrotation of said intermediate gear wheel means about a second axis whichis displaced and different from the first.

2. In a crane having at least one pair of rope drums in turn having gearwheels linked by a kinematic gear chain including a series ofcooperating elements, the improvements consisting in that said kinematicgear chain is a closed circuit kinematic chain drive having two seriesof components on opposite sides of and interconnected by a couplingshaft, each series of components, beginning at a point most distant fromsaid coupling shaft and in a direction toward said coupling shaft,including first gear means, motor means for driving said gear means, andbrake means for braking the drive in the event of motor failure; andsecond gear means comprising at least in part said gear wheels of saidrope drums and including standby means intermediate said gear wheels,said second gear means being operatively coupled to said first gearmeans of each said series of components for driving connectiontherewith, said standby means of said second gear means being mounted inrelation to said gear wheels to ac tively drive said gear wheels and tosupport the torque load only upon failure within said closed circuitkinematic chain drive of at least one of said series of components ofeach of said series, said standby means comprising for this purpose apair of intermediate gear wheels, at least one of which has adisplaceable mounting providing for rotation of said one of saidintermediate gear wheels about a first axis during normal operation ofsaid closed circuit kinematic chain, said mounting being automaticallydisplaced, upon failure of one of said series of components, in adirection transverse to the direction of meshing extent of saidintermediate gear wheels to orient said mounting for rotation of saidone intermediate gear wheel about a second axis which is displaced anddifferent from the first.

3. A crane according to claim 2, wherein means are provided in theregion of said mounting for actuating a warning device when saiddisplacement occurs.

4. A crane according to claim 3, wherein said displaceable mountingcomprises bearing means associated with said one intermediate gearwheel, said bearing means being received in slot means formed in a frameof the crane, said bearing means being constrained in its movement bysaid slot means.

5. A crane according to claim 2, wherein said slot means defines avertically extending slot.

6. A crane according to claim 3, wherein said displaceable mountingcomprises bearing means associated with said one intermediate gearwheel, said bearing means being mounted in resilient collar meanscarried by the crane frame, displacement of the axis about which saidone intermediate gear wheel rotates being accommodated by deformation ofsaid resilient collar means.

7. A crane according to claim 2, wherein said intermediate gear wheelsin said closed kinematic gear chain normally idle and are free ofworking load, said one of said intermediate gear wheels being displacedon asynchronous rotation of components of said kinematic chain, said oneintermediate gear wheel when displaced being effective to transferworking load torque as part of said kinematic chain.

8. A crane according to claim 7 wherein said displacement of said oneintermediate gear wheel is a limited displacement between a firstposition in which it normally idles to a second position constituting aposigagement with adjacent parts of said kinematic chain. i i i

1. In a crane having at least one pair of rope drums in turn having gearwheels linked by a kinematic gear chain including a series ofcooperating elements, the improvements consisting in that said kinematicgear chain is a closed circuit kinematic chain drive having two seriesof components on opposite sides of and interconnected by a couplingshaft, each series of components, beginning at a point most distant fromsaid coupling shaft and in a direction toward said coupling shaft,including first gear means, motor means for driving said gear means, andbrake means for braking the drive in the event of motor failure; andsecond gear means comprising at least in part said gear wheels of saidrope drums and including standby means intermediate said gear wheels,said second gear means being operatively coupled to said first gearmeans of each said series of components for driving connectiontherewith, said standby means of said second gear means being mounted inrelation to said gear wheels to actively drive said gear wheels and tosupport the torque load only upon failure within said closed circuitkinematic chain drive of at least one of said series of components ofeach of said series, said standby means comprising for this purposeintermediate gear wheel means having a displaceable mounting providingfor rotation of said first intermediate gear wheel means about a firstaxis during normal operation of said closed circuit kinematic chain,said mounting being automatically displaced, upon failure of one of saidseries of components, in a direction transverse to the direction ofmeshing extent of said intermediate gear wheel means to orient saidmounting for rotation of said intermediate gear wheel means about asecond axis which is displaced and different from the first.
 2. In acrane having at least one pair of rope drums in turn having gear wheelslinked by a kinematic gear chain including a series of cooperatingelements, the improvements consisting in that said kinematic gear chainis a closed circuit kinematic chain drive having two series ofcomponents on opposite sides of and interconnected by a coupling shaft,each series of components, beginning at a point most distant from saidcoupling shaft and in a direction toward said coupling shaft, includingfirst gear means, motor means for driving said gear means, and brakemeans for braking the drive in the event of motor failure; and secondgear means comprising at least in part said gear wheels of said ropedrums and including standby means intermediate said gear wheels, saidsecond gear means being operatively coupled to said first gear means ofeach said series of components for driving connection therewith, saidstandby means of said second gear means being mounted in relation tosaid gear wheels to actively drive said gear wheels and to support thetorque load only upon failure within said closed circuit kinematic chaindrive of at least one of said series of components of each of saidseries, said standby means comprising for this purpose a pair ofintermediate gear wheels, at least one of which has a displaceablemounting providing for rotation of said one of said intermediate gearwheels about a first axis during normal operation of said closed Circuitkinematic chain, said mounting being automatically displaced, uponfailure of one of said series of components, in a direction transverseto the direction of meshing extent of said intermediate gear wheels toorient said mounting for rotation of said one intermediate gear wheelabout a second axis which is displaced and different from the first. 3.A crane according to claim 2, wherein means are provided in the regionof said mounting for actuating a warning device when said displacementoccurs.
 4. A crane according to claim 3, wherein said displaceablemounting comprises bearing means associated with said one intermediategear wheel, said bearing means being received in slot means formed in aframe of the crane, said bearing means being constrained in its movementby said slot means.
 5. A crane according to claim 2, wherein said slotmeans defines a vertically extending slot.
 6. A crane according to claim3, wherein said displaceable mounting comprises bearing means associatedwith said one intermediate gear wheel, said bearing means being mountedin resilient collar means carried by the crane frame, displacement ofthe axis about which said one intermediate gear wheel rotates beingaccommodated by deformation of said resilient collar means.
 7. A craneaccording to claim 2, wherein said intermediate gear wheels in saidclosed kinematic gear chain normally idle and are free of working load,said one of said intermediate gear wheels being displaced onasynchronous rotation of components of said kinematic chain, said oneintermediate gear wheel when displaced being effective to transferworking load torque as part of said kinematic chain.
 8. A craneaccording to claim 7 wherein said displacement of said one intermediategear wheel is a limited displacement between a first position in whichit normally idles to a second position constituting a position on eitherof opposite sides of said first position, the side of said firstposition to which said one gear means is moved depending on the angularsense of said asynchronous rotation, said one intermediate gear wheeltransferring working load torque in either of said second positions aspart of said kinematic chain, and warning means responsive to saiddisplacement in either said sense.
 9. A crance according to claim 8,wherein said intermediate gear wheels are normally in loose meshingengagement with adjacent parts of said kinematic chain.